1. Technical Field of the Invention
The present invention relates to a vibration generating device used for a call or the like of a small wireless machine, for example, a portable or mobile telephone.
2. Prior Art
In recent years, as a kind of a small wireless machine, such as a paging system small wireless calling machine, a PHS, or a portable, mobile telephone, a machine of a type having a built-in vibration generating device made by eccentrically coupling a vibrator of high specific gravity metal to a rotating shaft of a motor has become popular. According to the small wireless calling machine or the like having such a built-in vibration generating device, instead of generation of a ringing tone, a vibration is generated by the rotation of the vibrator so that it is possible to confirm reception without knowledge by another person even in, for example, a crowd or a meeting.
Conventionally, the vibration generating device of this kind of small wireless machine is constructed such that a vibrator of a non-cylindrical shape is integrally coupled with a rotating shaft of a small motor connected to a signal generating circuit of the small wireless machine. This vibrator is made of a high specific gravity metal molded by performing a powder metallurgical method. A cylindrical boss portion is integrally formed at an eccentric load portion of a substantially fan-shaped section. A rotating shaft is inserted into an attachment hole formed in the boos portion, and the boss portion is plastically deformed by caulking, so that the boss portion and the rotating shaft are drawn close to each other, whereby the vibrator is integrally coupled to the rotating shaft.
According to the conventional vibration generating device of this type, since the vibrator itself is caulked and is directly coupled to the rotating shaft, as compared with another conventional vibration generating device in which a vibrator is fixed to a rotating shaft through an adhesive or other coupling manner, there is merit in that it becomes possible to reduce the number of parts of the vibrating generating device.
However, in the above conventional vibration generating device, since the attachment hole must be formed in the inside of the cylindrical boss portion of the vibrator, there has been a problem in that when the vibrator is molded by pressing a powder raw material, it is difficult to fill the powder raw material into the boss portion, especially in a shaping die portion of the boss portion having a thin outer periphery, and the yield of the vibrator is lowered.
Additionally, for the purpose of satisfying a demand for miniaturization in recent years, an attempt has been made to form the vibrator itself to be small. However, since the boss portion around the attachment hole becomes very thin, there has also been another problem in that when caulking is performed by applying a large force, a crack is likely to be generated. On the other hand, if the caulking force is low, a desired pull-out strength cannot be obtained, with the result that the adjustment of the caulking force becomes difficult.
As another conventional vibration generating device, there has been a proposal like that as shown in FIG. 10 and FIG. 11. A groove portion 4, in which a rotating shaft 3 is fit, is formed at a central portion of an eccentric load portion 2 of a vibrator 1. Side walls 5, which define both side edge portions of the groove portion 4, are integrally formed with and extend from the eccentric load portion 2 along the groove portion 4. The central portions of tip portions of the side walls 5, in an axial line direction, are caulked from an opening side of the groove portion 4 toward a bottom side thereof by a caulking punch 7. The tip end of the caulking punch 7 is shaped into an R shape (or round shape) or a rectangular parallelepiped shape, so that the vibrator 1 becomes integrally coupled to the rotating shaft 3.
According to the conventional vibration generating device described above, there are merits in that molding is easier than with the vibrator including the boss portion in which the attachment hole is formed, so that manufacture yield can be improved. Even in the case where the vibrator 1 itself becomes small, as compared with the case where the thin portion such as the outer periphery of the boss portion is caulked, there is little fear that a crack is generated.
However, in the conventional vibration generating device shown in FIGS. 10 and 11, when the tip portion end surfaces of the side walls 5 are caulked, the entire width dimensions from sides of the groove 4 to sides or outer peripheries 6 of the side walls 5 are crushed and, therefore, a high caulking force is required. However, since the rigidity of the portions of the side walls 5 at the sides of the groove 4 is high, because of the rotating shaft 3, when plastic deformation lei performed, bulging or deformation is mainly caused toward the sides or the outer peripheries 6 which become free ends, and as a result, there has been a problem in that a high pull-out strength cannot be obtained. Besides, as a result of a high caulking force being required, when an attempt to increase a tungsten content is made to obtain a desired vibration, even in the case where the vibrator 1 is made small in diameter, it becomes brittle, so that there has also been a problem that a crack is likely to be generated in the caulked side walls 5.
The present invention has been made in view of the above, and a principal object of the present invention is to provide an improvement in a vibration generating device for a small wireless machine.
Another object of the present invention is to provide a vibration generating device of a small wireless machine in which manufacture of a vibrator is easy, the vibrator can be coupled to a rotating shaft of a motor at a high pull-out strength even by employing a low caulking force, and the whole device can be further miniaturized.
According to a first aspect of the invention there is provided a vibration generating device of a small wireless machine which includes a vibrator integrally coupled to a rotating shaft of a motor, wherein a groove portion in which the rotating shaft is fitted is formed in an eccentric load portion. Side walls extending from the eccentric load portion, and forming both side edge portions of this groove portion are provided. And, a portion of a tip portion end surface of these side walls, except at an outer peripheral portion of the side walls and at a aide of the groove portion, is caulked from an opening side of the groove portion toward a bottom side of the groove portion, so that the vibrator is integrally coupled to the rotating shaft.
According to a second aspect of the invention there is provided a vibration generating device of a small wireless machine in which a vibrator is integrally coupled to a rotating shaft of a motor, wherein an eccentric load portion is formed into a truncated fan shape in which a central angle is less than 180xc2x0. Accordingly, the eccentric load portion has a flat surface at a rotational central side. A groove portion in which the rotating shaft is fitted is formed in the flat surface. Side walls forming both side edge portions of this groove portion are provided. A portion of the flat surface, except at an outer peripheral side portion of the side wails and at a side of the groove portion, is caulked from an opening side of the groove portion toward a bottom side of the groove portion, so that the vibrator is integrally coupled to the rotating shaft.
Further, according to a third aspect of the invention, which is a modification of the first aspect or second aspect of the invention, there is provided a vibration generating device of a small wireless machine, wherein a caulked portion formed into a concave shape in the tip portion end surface of the first aspect or the flat surface of the second aspect, respectively, by caulking from the opening side of the groove portion toward the bottom side thereof is formed so that a length dimension at the side of the groove portion in an axial line direction is longer than a length dimension at an outer peripheral side of the groove portion.
According to a fourth aspect of the invention, in a width dimension W of the tip portion end surface or the flat surface as recited in any one of the first to third aspects, from the side of the groove portion to the outer peripheral side thereof, a range of 0.25 W to 0.9 W from an edge portion at the side of the groove portion is caulked.
Further, according to a fifth aspect of the invention, the groove portion of the vibrator as recited in any one of the first to fourth aspects is formed to have such a size as to internally contain a range exceeding a central angle of 180xc2x0 of the rotating shaft. And, an opening width W1 of the groove portion is set so that a ratio of W1 to a diameter D of the rotating shaft of the motor (W1/D) is in a range of 0.70 to 0.95.
In the vibration generating device of the small wireless machine as recited in any one of the first to fifth aspects of the invention, the rotating shaft of the motor is fitted in the groove portion, and in the tip portion end surfaces or the flat surfaces of the side walls forming both side edge portions of this groove portion, the portion, except at the outer peripheral side portion and at the side of the groove portion, is caulked toward the bottom side of the groove portion. Accordingly, as compared with the conventional vibration generating device shown in FIG. 10 and FIG. 11, it becomes possible to couple the vibrator to the rotating shaft by employing a lower caulking force. At the same time, the outer peripheral portion of the side walls which are not caulked function as wall portions against the plastic deformation in the caulked portion, and consequently, the greater part of the caulked portion is extended over the groove portion. Then, the vibrator is firmly fixed to the rotating shaft at three points, i.e. the bottom portion of the groove portion, and both of the extended side walls. Thus, according to the vibration generating device of the present invention, the manufacture of the vibration generating device is easy, and further, it is possible to couple the vibrator to the rotating shaft of the motor at a high pull-out strength even by employing a lower caulking force.
From the above, according to the vibration generating device of the present invention (as recited in any one of the first to fifth aspects), since the vibrator can be firmly fixed to the rotating shaft of the motor by employing a lower caulking force than that of the prior art, it is possible to realize miniaturization and lightening of the vibrator, as well as miniaturization and lightening of the vibration generating device and the entirety of the small wireless machine. Additionally, because the caulking load can be made small generation of a crack in the vibrator can be prevented, productivity of the vibration generating device is improved, and it becomes possible to improve the vibration efficiency by realization of the high specific gravity of the vibrator.
Here, especially in the third aspect of the invention described above, the length dimension of the caulked portion in the axial line direction at the side of the groove portion, where most portions are extended toward the side of the rotating shaft, becomes larger than that at the peripheral side of the groove portion which functions as the wall portion when the caulked portion is plastically deformed. Accordingly, the vibrator can be coupled to the rotating shaft of the motor at a high pull-out strength by employing a lower caulking force. In addition, it becomes possible to use a caulking punch which can be easily manufactured and has a circular shape in cross section, and the use life of the caulking punch can be greatly lengthened.
The fourth aspect of the invention is based upon any one of the first to third aspects of the invention described above. Namely, in the tip portion end surface or the flat surface of the side walls, when the portion, except at the outer peripheral side portions of the groove portion and at the groove sides, is caulked toward the bottom side of the groove portion, in the width dimension W of the tip portion end surface or the flat surface from the groove side to the outer peripheral side of the groove portion, it is preferable to caulk the range of 0.25 W to 0.9 W from the edge portion of the side of the groove portion. At this time, in the case where the caulking width dimension is small, it is sufficient if the caulking length dimension in the axial line direction is made large, and on the contrary, in the case where the caulking width dimension is large, even if the caulking length dimension in the axial line direction is small, a sufficient pull-out strength can be obtained. The range of caulking is limited to the range of 0.25 W to 0.9 W because, if the range is smaller than 0.25 W it becomes difficult to obtain a sufficient plastic deformation amount to firmly fix the vibrator to the rotating shaft of the motor, and if the range exceeds 0.9 W the foregoing function of the wall portion counteracting the plastic deformation of the caulked portion is decreased, and as a result, the outer peripheral portion is also forcibly deformed outwardly such that the pull-out strength is lowered.
Additionally, the shapes of the side walls may be formed so that the entirety of the groove portion becomes U-shaped by erecting the side walls from both side edges. In this case, in the state where the rotating shaft is fitted in the groove portion, the rotating shaft is internally contained in the groove portion within the range of a central angle of 180xc2x0. On the other hand, like with the fifth aspect of the invention, when the groove portion of the vibrator is formed to have such a size that the range of the central angle of 180xc2x0 or more of the rotating shaft is internally contained, and the opening width W1 of the groove portion is set so that the ratio of W1 to the diameter D of the rotating shaft (w1/P) becomes within the range of 0.70 to 0.95 as a result of the plastic deformation of the side wall after caulking, it is possible to fill the opening portion of the groove portion more effectively and to firmly fix the vibrator, which is preferable.